1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a magnetic recording head, and more particularly, to a metal layer having a C-shaped nano-aperture, a method of forming the same, a light delivery module including the metal layer, and a heat assisted magnetic recording head including the same.
2. Description of the Related Art
As technologies for magnetic recording heads and magnetic recording methods become more highly developed, the recording density of magnetic recording media increases. However, an increase in recording density causes a decrease in an area of the magnetic recording medium in which minimum unit information is recorded, namely, a bit size, which causes the bit size to be affected by a super-paramagnetic effect. Consequently, thermal instability of the bit size in the magnetic recording medium is worsened, which makes it difficult to implement a higher recording density.
To achieve high thermal stability of data, a material having a strong coercive force is commonly used as the magnetic recording medium. When a material having a strong coercive force is used, a stronger magnetic field is needed to record data. However, since at a certain point the intensity of the magnetic field generated from the magnetic recording head becomes saturated, a material having a strong coercive force may cause difficulties in recording.
The aforementioned problem may be solved to some degree by using a heat assisted magnetic recording (hereinafter, referred to as HAMR) method in which an area where data is to be recorded is heated before recording data to the heated region.
In the HAMR method, a light delivery module is used as a unit for heating a data recording region. The light delivery module includes a light waveguide transmitting light generated by a light source such as a laser diode. A nano aperture is provided at a light exit surface, which generates an enhanced near field by changing the energy distribution of the transmitted light.
Since the data recording region is heated to near the Curie temperature in the HAMR method, the light delivery module provided in the magnetic recording head used in the HAMR method should be able to emit light having an intensity high enough to perform heating while having a small spot size so as to increase a recording density.
Recently, various types of a light delivery module for the HAMR method have been proposed, and most of them include a square aperture, a circular aperture or a C-shaped aperture.
As for a light delivery module including the square aperture or the circular aperture, when an aperture size is smaller than 1% of a wavelength of incident light, the optical power throughput decreases in proportion to (wavelength)−4.
As for a light delivery module including the C-shaped aperture, a main pole of a magnetic head may be used as a ridge of the aperture. In this case, the distance between a magnetic field and light may be minimized, but a magnetic characteristic of the main pole may be lowered due to heat.
However, the shape and the size of a nano aperture have not been optimized for maximum near field enhancement. In particular, since the coupling efficiency between an exit surface of the waveguide and an inlet of a nano aperture, and a light spot profile at an outlet of the nano aperture are individually taken into account, the shape and the size of the nano aperture cannot be optimized. Therefore, a break from the structural simplicity of the related art nano aperture should be attempted in order to reduce the size of a light spot and maximize a near field enhancement effect.